CONVENTIONAL microwave transmitter designs are based on modulation at
the intermediate frequency (IF), requiring a complex chain of mixers,
filters, and amplifiers to upconvert the modulated signal to the trans
mission frequency. By applying direct modulation of the microwave carr
ier signal, a significant reduction in system hardware requirements is
achieved. A single-chip transmitter design for indoor radio communica
tions provides direct-carrier modulation in the 17/18-GHz frequency ra
nge, employing a microwave-monolithic-integrated-circuit (MMIC) phase
shifter and variable attenuator to provide phase and amplitude control
. This second part of a two-part article presents the physical realiza
tion of the phase-and amplitude-control circuits-which are implemented
with a voltage-controlled oscillator (VCO) and 360-deg, phase shifter
on one chip and an amplitude modulator on a separate chip. The struct
ure and performance of the balanced vector modulator (which is realize
d by cascading two amplitude biphase modulators) will also be describe
d.